Exhaust process and system and cooling of gases from thermodynamic machines on ships

ABSTRACT

The system according to the invention prevents the effect of turbulence due to exhaust of gases via chimney from propulsion machines on aircraft carriers ( 1 ).  
     It consists of creating internal circulation of water by means of a scope ( 3 ) of a circulation pump ( 4 ), an inlet chamber ( 6 ) in which exhaust gases from the thermodynamic machines of the Ship empty. Water nozzles are placed in this inlet chamber ( 6 ). The resulting mixture is evacuated via a pipe ( 7 ) and a mixing tube ( 8 ) terminating outside the ship, to the stern thereof, just above the water line. Application to aircraft carriers.

FIELD OF THE INVENTION

The invention concerns ships propelled by thermodynamic machines, such as, inter alia, gas turbines and internal combustion engines discharging high-temperature gases. A particularly advantageous application is provided for aircraft carriers.

PRIOR ART AND PROBLEM

On ships of average and high tonnage, exhaust gases from thermodynamic propulsion machines, such as gas turbines and internal combustion engines, are evacuated by means of large-sized chimneys surmounting the entire upper structure of the ship. The gases thus evacuated are, at the level of these chimneys, several hundred degrees C. in temperature, approximately 500° C. This presents disadvantages common to all types of ships, such as creation of one or more hot points, risk of fire, loss of space in the upper part of the structure of the ship. For warships, there is the added disadvantage due to the loss of stealth associated with the emission of infrared waves due to temperature. Finally, for aircraft carriers, evacuation via these chimneys causes generation of currents of ascending warm air, in turn generating dangerous turbulence for planes in the landing phase and possibly in the takeoff phase.

The aim of the invention is to rectify these disadvantages by proposing another way of evacuating exhaust gases from such thermodynamic machines on ships.

SUMMARY OF THE INVENTION

To this end a first principal object of the invention is a process for exhaust and cooling of exhaust gases from thermodynamic machines provided for propelling a ship, the process consisting of cooling the exhaust gas by mixing in water on which the ship manoeuvres.

The principal embodiment provides creating natural circulation of water inside the ship, from the prow to the stern, for cool processing by mixing gases in water which is injected into the gases, such injection taking place in an inlet chamber by means of several nozzles to homogenise the mixture, this mixture being advantageously made by means of a mixing tube where the mixing pipes emerge, in the aim of lowering the pressure and thus recovering energy, and evacuation of the mixture thus obtained takes place just above the water line.

This process can be improved by using forced injection of water, for example using a circulation pump.

For the purpose of improving this mixture, it is advantageous to prolong the latter over a certain distance prior to evacuation of the mixture.

It is likewise provided to be able to extract a portion of the heat from the exhaust gases, at the outlet of the thermodynamic machines, by means of a heat exchanger, with the aim of supplying auxiliary operating power to the ship.

A second principal object of the invention is a system for exhausting and cooling exhaust gases from thermodynamic propulsion machines of a ship, mainly comprising:

-   -   an exhaust collector of exhaust gases;     -   an inlet scope for water in the lower part of the ship;     -   an inlet pipe for conveying water into an inlet gas chamber;     -   at least one water nozzle at the outlet of the inlet pipe, in         the inlet chamber; and     -   a mixing pipe terminating outside the ship, to the rear relative         to the inlet scope.

The principal embodiment provides utilising a circulation pump in the water inlet pipe to force the admission of water.

It is advantageous to use a mixer head at the outlet of the inlet chamber, at the level of at least one nozzle.

According to the present invention several water nozzles are placed in the inlet chamber, the mixing pipe has a length equal to approximately six times its diameter at the outlet of the inlet chamber, a mixing tube is used at the outlet of the mixing pipe with the aim of lowering the pressure of the mixture at this level, and the mixture exits at the stern of the ship, below the water line, in such a way as not to cause rising air movements.

LIST OF FIGURES

The invention and its technical characteristics will be better understood from reading the detailed description of an embodiment of the invention, accompanied by three figures, where respectively:

FIG. 1 illustrates a diagram relative to the process and the system according to the invention;

FIG. 2 schematically illustrates a ship on which is installed the system according to the invention; and

FIG. 3 schematically illustrates the stern of the ship on which is installed the system according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

In reference to FIG. 1, the system according to the invention comprises a scope 3 whereof the opening is turned to the front of the ship, that is, when the latter advances, such that water enters it. The utilisation of such a scope 3 allows the water circuit to advantageously trap water by benefiting from the effect of the wake of the ship at high speed. It is prolonged by an internal water inlet pipe 5 on the ship. Placed on the latter or in front of same is a circulation pump 4 for reinforcing the injection of water into the water inlet pipe 5 which acts as an ejector exhaust pipe.

On the other hand, exhaust gases from thermodynamic machines for propelling the ship, namely diesel or gas turbine motors are collected in a gases exhaust collector 11. The latter terminates in an inlet chamber 6, in which water nozzles 12 are also installed where the water inlet pipe 5 terminates. The inlet chamber 6 is advantageously equipped with a mixer head 13 which helps accelerate the exhaust gases. This mixer head 13 terminates in a radial plane of the inlet chamber 6 in which the water nozzles 12 terminate.

The velocity of water in the internal water inlet pipe 5 produces low pressure in the inlet chamber 6, which favours the escape of exhaust gases from the machines.

At the exit to this inlet chamber 6 is an internal mixing pipe 7 in which the double-phase mixing of exhaust gases and trapped water takes place over a certain length. In effect, to this end, this mixing pipe 7 has a length approximately six times greater than its diameter. In order to diminish the force dissipated by such a process, by means of this system, a mixing tube 8 is placed at the outlet of the mixing pipe 7 to slow down the double-phase mixing and to recover maximum pressure. During this slow-down phase, exhaust gases whose temperature at the outlet of the machines can reach 500° C., are cooled by contact to a temperature approaching that of the trapped water. It is thus envisaged to trap water at 15° and to reject double-phase mixing at 25°.

FIG. 2 schematically illustrates a ship of large tonnage, namely an aircraft carrier 1, surmounted with its upper structure 2, without a chimney. The system according to the invention is placed in 1 a lower part of the aircraft carrier 1, to the stern thereof. The scope 3 is immersed to the level of the lower part of the hull, the circulation pump 4 is placed inside the aircraft carrier. The terminal part of the system, constituted by the inlet chamber 6, of the mixing pipe 7 and of the mixing tube 8 can be placed outside the hull of the ship. The mixing tube 8 is placed just above the water surface, below the level of the bridge 17 of the aircraft carrier 1.

In reference to FIG. 3, the system according to the invention is installed in the stern region of the aircraft carrier 1, below the bridge 13 thereof. This figure illustrates four thermodynamic machines 14, for example diesel motors whereof exhaust gases are collected via exhaust tubes 15. Each of them terminates in a exchanger 16 of the high-temperature type, which helps trap a part of the thermal energy originating from these exhaust gases, with the aim of operating machine installations or devices of the aircraft carrier 1. A particular example is the propulsion catapults for the aircraft. In effect, it is possible to extract 10 to 20% of the energy from these gases to feed the catapults with steam. The gases, thus partially cooled, but still at a temperature of several hundred degrees Celsius, are conveyed by exhaust collectors 11, each terminating in an inlet chamber 6.

It is notes that a system according to the invention has been installed on each side of the aircraft carrier 1. The mixing pipe 7 and the mixing tube 8 are placed outside the hull of the ship. This is only one possible embodiment of the invention, the process capable of being adapted to the power of each of the ships on which it is to be utilised, especially by adapting the number of systems to the number of machines.

With the process according to the invention it is conceivable that the effects of turbulence due to exhaust from chimneys on traditional aircraft carriers are eliminated. This offers an enormous advantage for pilots when landing on aircraft carriers. In addition, the infrared signature of the ship is considerably reduced. 

1. A process for exhausting and cooling exhaust gases from thermodynamic machines (14) of a ship, consisting of cooling exhaust gases by mixing with water on which the ship is floating, characterised in that injection of water takes place in an inlet chamber (6) by means of several water nozzles (12), and in that it consists of: recovering the energy at the outlet of the system by means of a mixing tube (8), mixing the exhaust gas and water at the outlet of the inlet chamber (6) in a mixing pipe (7) over a certain length; and evacuating the mixture obtained just above the water line of the ship (1).
 2. The process as claimed in claim 1, characterised in that it consists of creating natural circulation of water inside the ship, from the prow to the stern for cool processing by mixing exhaust gases into which water is injected.
 3. The process as claimed in claim 2, characterised in that the injection of water is forced by a circulation pump (4).
 4. A system for exhausting and cooling exhaust gases from thermodynamic machines (14) on a ship (1) comprising: an exhaust collector of gases (11) from the thermodynamic machines (14) propelling the ship; a scope (3) for admitting water, placed in the lower part of the ship (1); a water inlet pipe (5) at the outlet of the scope (3); an inlet chamber (6) for exhaust gases, placed at the end of the water inlet pipe (5); a mixing pipe (7) placed at the outlet of the inlet chamber (6) and terminating at the stern of the ship (1) relative to the scope (3), characterised in that it comprises: a mixing tube (8), placed at the outlet of the mixing pipe (7), several water nozzles (12) placed in the inlet chamber, in that the mixing pipe (7) has a length equal to approximately six times its diameter, and in that the outlet of the system terminates at the stern of the ship (1), just above the water line of the ship (1).
 5. The system as claimed in claim 4, characterised in that it comprises a circulation pump (4) placed at the inlet of the inlet pipe (5).
 6. The system as claimed in claim 4, characterised in that it comprises a mixer head (13) in the inlet chamber (6) at the level of at least one water nozzle (12). 